System and Method for Furnace Fluid Flow Management

ABSTRACT

A furnace has a primary heat exchanger tube, a secondary heat exchanger comprising a plurality of secondary heat exchanger tubes, a hot header configured to provide a fluid flow path between an output of the primary heat exchanger tube to an input of the secondary heat exchanger, and a perforated fluid flow plate disposed at least partially within the hot header.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119(e) to U.S.Provisional Patent Application No. 61/828,117 filed on May 28, 2013 byHanks, et al. and entitled “System and Method for Furnace Fluid FlowManagement,” the disclosure of which is hereby incorporated by referencein its entirety.

BACKGROUND

Some heating, ventilation, and/or air conditioning (HVAC) systemscomprise furnaces that generate condensation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an orthogonal right side view of a furnace according to thedisclosure.

FIG. 2 is an oblique front-left view of a portion of the furnace of FIG.1.

FIG. 3 is an oblique rear-right view of the portion of the furnace ofFIG. 2.

FIG. 4 is a partially exploded oblique front-left view of the portion ofthe furnace of FIG. 2.

FIG. 5 is a partially exploded oblique rear-right view of the portion ofthe furnace of FIG. 2.

FIG. 6 is another partially exploded oblique front-left view of theportion of the furnace of FIG. 2.

FIG. 7 is another partially exploded oblique rear-right view of theportion of the furnace of FIG. 2.

FIG. 8 is another partially exploded oblique front-left view of theportion of the furnace of FIG. 2.

FIG. 9 is another partially exploded oblique rear-right view of theportion of the furnace of FIG. 2.

FIG. 10 is another partially exploded oblique front-left view of theportion of the furnace of FIG. 2.

FIG. 11 is another partially exploded oblique rear-right view of theportion of the furnace of FIG. 2.

FIG. 12 is an oblique rear-left view of another portion of the furnaceof FIG. 1.

FIG. 13 is an orthogonal rear view of another portion of the furnace ofFIG. 1.

FIG. 14 is an orthogonal rear view of another portion of the furnace ofFIG. 1 comprising an alternative embodiment of a gasket.

FIGS. 15-17 are oblique views of alternative embodiments of perforatedfluid flow plates.

FIGS. 18-20 are oblique partially exploded, orthogonal cutaway rightside, and an orthogonal right side detail views, respectively, ofalternative embodiment of a furnace according to the disclosure.

FIGS. 21-23 are oblique partial, oblique partially exploded, andorthogonal right side views, respectively, of another alternativeembodiment of a furnace according to the disclosure.

DETAILED DESCRIPTION

Condensing furnaces may produce many gallons of condensate per hour, andthat condensate may accumulate in the furnace and damage the furnace. Inaddition, standing condensate may promote bacterial growth. Further,repeated volatilization and/or evaporation of corrosive, acidic, and/orbasic fluids may corrode and/or cause pitting of metallic components ofa furnace. In some embodiments of this disclosure, a condensinggas-fired furnace is provided that manages fluid flow including hotcombustion gasses and condensation.

Referring now to FIGS. 1-13, show a condensing gas-fired furnace 100 (invarious stages of assembly/disassembly) according to an embodiment ofthe disclosure. In this embodiment, the furnace 100 is configured as anindoor furnace 100 that provides conditioned, heated air to an interiorspace. The components of the furnace 100, however, may be equallyemployed in an outdoor or weatherized furnace to condition an interiorspace. Moreover, the furnace 100 may be used in residential orcommercial applications. The furnace 100 may generally comprise a frontside 102, rear side 104, left side 106, right side 108, top side 110,and bottom side 112.

In this embodiment, the furnace 100 may comprise a burner assembly 114,a plurality of primary heat exchangers 116, and a finned, condensing,secondary heat exchanger 118. The primary heat exchangers 116 may extendfrom the burner assembly 114 to the secondary heat exchanger 118. Inthis embodiment, each burner assembly 114 may comprise an associatedprimary heat exchanger 116 for venting hot flue gases such that theprimary heat exchanger 116 is in the combustion airflow path of itsassociated burner assembly 114. In general, the total number of burnerassemblies 114 and/or heat exchangers 116 may vary depending upon thedesired capacity of the furnace 100. Each primary heat exchanger 116 maycomprise a bent, S-shaped tubular member that extends through a tortuouspath to enhance the surface area available for heat transfer with thesurrounding circulation air. Each primary heat exchanger 116 maycomprise a first open end 120 defining a flue gas inlet and a secondopen end 122 defining a flue gas outlet. The second open end 122 of eachprimary heat exchanger 116 may feed the secondary heat exchanger 118 sothat the primary heat exchangers 116 transport hot flue gases to thesecondary heat exchanger 118. Although the primary heat exchangers 116are tubular in some embodiments, the primary heat exchangers 116 maycomprise, for example, clamshell, drum, shell and tube-type, and/or anyother suitable type of heat exchangers.

In general, combustion air may be introduced into the furnace 100 eitherin induced draft mode by pulling air through the system or in forceddraft mode by pushing air through the system. In this embodiment,induced draft mode may be employed by pulling the hot flue gases fromthe secondary heat exchanger 118 with a blower or fan 124 by creating arelatively lower pressure at the exhaust of the secondary heat exchanger118. A control system may control the blower or fan 124 to anappropriate speed to achieve adequate air flow for a desired firing ratethrough the burner assemblies 114. Increasing the fan speed of theblower or fan 124 may introduce more air to the air/fuel mixture,thereby changing the characteristics of the combustion within the burnerassemblies 114.

A circulation blower may blow circulation air across the primary heatexchangers 116 and the secondary heat exchanger 118 to enable thetransfer of thermal energy from the primary heat exchangers 116 and thesecondary heat exchanger 118 to the air. The heated, exiting airflow maythen be distributed to a conditioned area. The furnace 100 is shown in afirst orientation in which the circulation blower is nearer the bottomside 112 of the furnace 100 relative to the primary heat exchangers 116and blows the circulation air across the primary heat exchangers 116 andup toward the top side 110 of the furnace 100.

While moving through the primary heat exchangers 116 and then thesecondary heat exchanger 118, the hot flue gases may begin to cool andcontinue cooling as they move through the secondary heat exchanger 118,a cold header 126, and then the blower or fan 124. Finally, the fluegases may move through an exit pipe 125 and then through a flue pipe(not shown) to exit out of the flue pipe and to the outside environment.As the flue gases cool throughout the secondary heat exchanger 118, theflue gases may cool below a dew point temperature of the water vapor,which may be mixed with corrosive combustion products, producing acorrosive condensate. Accordingly, this system may be referred to as acondensing gas-fired furnace 100. The cold header 126 may provide adrainage path for managing and/or draining the condensate and/or anyother liquid. In some cases, the condensate may form within and/or flowthrough tubes 128 of the secondary heat exchanger 118. The secondaryheat exchanger 118 may further comprise fins 130, an input end plate132, and an output end plate 134. The tubes 128 may comprise a corrosionresistant metal, such as, but not limited to 29-4C stainless steel, 2205stainless steel, T140 aluminized steel, and/or any other suitablecorrosion resistant material. The furnace 100 may further comprise a hotheader cover 136 that joins to a hot side panel 138. The hot side panel138 may comprise apertures 140 for receiving hot combustion gasses fromthe primary heat exchangers 116 into a space between the hot headercover 136 and the hot side panel 138.

Further, a fluid flow plate 142 may be disposed between the secondaryheat exchanger 118 and the hot header cover 136 so that fluid must passthrough flow apertures 144 of the fluid flow plate 142 to pass from thehot header space bound by the hot header cover 136 and the secondaryheat exchanger 118. In some embodiments, the flow apertures 144 arelongitudinally (in a front-back direction) misaligned with the tubes 128of the secondary heat exchanger 118 as shown in FIGS. 13 and 14. It willbe appreciated that selection of the sizes of the various flow apertures144, relative location of the flow apertures 144 relative to each other,the tubes 128, an intake of the fan 124 may affect a homogeneity offluid flow distribution amongst the tubes 128 as well as upstream withinthe primary heat exchangers 116. This disclosure contemplates providinga plurality of the flow apertures 144 rather than a single largeslot-like aperture in the fluid flow plate 142. In some embodiments,gaskets 146 may be used to seal between components and offsetcomponents. Gaskets 146 may comprise any suitable material configured toform a substantially fluid-tight seal between components, such as, butnot limited to, silicone, plastic, and/or any other material configuredto withstand relatively high temperatures, such as, but not limited to,up to about 850 degrees Fahrenheit.

Not only does the fluid flow plate 142 homogenize gaseous fluid flow,but the form, and shape of the fluid flow plate 142 may be selected tominimize and/or eliminate condensation collection and/or buildup withinthe fluid flow plate 142. As shown in FIG. 13 outermost located tubes128′ may be configured to abut the interior wall of the fluid flow plate142 so that condensation that may enter the fluid flow plate 142 will bedrained into the tubes 128′ when the furnace 100 is properly installed.Further, in this embodiment, the temperatures of operation near thefluid flow plate 142 are such that condensation formation in and/or nearthe fluid flow plate 142 is minimized and/or eliminated when the furnace100 is operating properly.

In some embodiments, the secondary heat exchanger 118 may be modular innature insofar as it is removable from the primary heat exchangers 116in a non-destructive manner. Particularly, in some embodiments, the hotside panel 138 of the secondary heat exchanger 118 may comprise fastenerholes configured to receive fasteners such as, but not limited to,stainless steel screws, bolts, and/or any other suitable fastener thatallows for relatively easy assembly and/or disassembly of the secondaryheat exchanger 118 to a component, such as, but not limited to, a hotheader cover 136 that forms a portion of the fluid flow path between theprimary heat exchangers 116 and the secondary heat exchanger 118. Thecomponents of furnace 100 comprise other fastener holes that similarlyaide in allowing the secondary heat exchanger 118 to be selectivelyremovable from the primary heat exchangers 116 in a modular manner. Themodular nature of the secondary heat exchanger 118 being easilyremovable from the primary heat exchanger 116 and/or the components thatjoin the secondary heat exchanger 118 to the primary heat exchanger 116allow for replacement and/or repair of the secondary heat exchanger 118without the need to replace the primary heat exchanger 116.

Referring now to FIG. 14, an embodiment of a guide gasket 300 is shown.The guide gasket 300 may comprise any suitable material configured toform a substantially fluid-tight seal between at least one of the tubes128 and the fluid flow plate 142. The guide gasket 300 is configured tocomprise inclined surfaces 302 such that any introduction ofcondensation or liquid into the fluid flow plate 142 will be guided bygravity to the outermost tubes 128 and so that the lowest availablespace within the fluid flow plate 142, regardless of orientation, is asurface configured to drain liquid out of the fluid flow plate 142 andinto tubes 128. In some embodiments, the guide gasket 300 may fill aninterior volume of the fluid flow plate 142 so that when the furnace 100is substantially properly oriented relative to gravity, any flowingliquids are guided along the guide gasket 300 into a tube 128 and sothat liquids are not allowed to pool, stagnate, and/or otherwise remainwithin the fluid flow plate 142.

FIG. 15 is an alternative embodiment of a fluid flow plate 400 that isconfigured to comprise integral inclined surfaces 402 that areconfigured to drain liquids to liquid outlets 404 that may be connectedto tubes 128″. The fluid flow plate 400 further comprises flow apertures408 configured to allow combustion fluids therethrough.

FIG. 16 is an alternative embodiment of a fluid flow plate 500 that isconfigured to comprise integral inclined surfaces 502 that areconfigured to drain liquids to liquid outlets 504 that may be connectedto tubes such as tubes 128″. The fluid flow plate 500 further comprisesflow apertures 506 configured to allow combustion fluids therethrough.

With regard to each of the fluid flow plates 142, 400, 500 and the guidegasket 300, at least four substantially orthogonal orientations for thefurnace 100 are contemplated, each with the front 102 and back 104remaining generally parallel to the ground so that gravity can drawliquids out of the fluid flow plates 142, 400, 500 and the guide gasket300 in a variety of orientations.

Referring now to FIG. 17, a schematic front view of a fluid flow plate142 is shown as comprising apertures 144. However, in some embodiments,apertures 144′ which may be directly longitudinally within a profile orlongitudinal footprint 600 of a fan 124 inlet may not be provided. Insome cases, by not providing apertures 144′ longitudinally aligned withthe longitudinal footprint 600, fluid flow through the apertures 144 ofthe fluid flow plate 142 may be forced to homogenize and/or otherwisemore equally distribute in mass flow rate through the apertures 144.

Referring now to FIGS. 18-20, an oblique partially exploded view, anorthogonal cutaway right side view, and an orthogonal right side detailview of alternative embodiment of a furnace 700 are shown, respectively.The furnace 700 is substantially similar to furnace 100 insofar as itgenerally comprises burner assemblies 714, primary heat exchangers 716,a secondary heat exchanger 718, a fan 724, and a cold header 726. Thisembodiment comprises a secondary heat exchanger header plate 728 towhich secondary heat exchanger tubes 730 are joined and/or through whichsecondary heat exchanger tubes 730 extend through. In this embodiment,the secondary heat exchanger tubes 730 extend through the secondary heatexchanger header plate 728 and are flanged on the ends and/or swaged. Inthis embodiment, a perforated cover plate 732 is captured between afirst seal 734 and a second seal 736. The first seal 734 is capturedbetween the header plate 728 and the perforated cover plate 732. Thesecond seal 736 is captured between the perforated cover plate 732 and ahot header primary plate 738. A third seal 740 is captured between thehot header primary plate 738 and a hot header collector box 742. In somecases, the above-described embodiment may lower air flow noise as afunction of an increased distance provided between a circulation bloweroutlet and the secondary heat exchanger 718. In some cases, theabove-described embodiment may provide for an increased vertical heightdifferential between the rear and front ends of the secondary heatexchanger tubes 730 so that condensate drainage is improved and/orbetter provided for. In some cases, the above-described embodiment mayprovide a relatively smaller overall furnace. In some cases, theabove-described embodiment may be configured so that only insignificantamounts of condensate or no condensate forms on the hot side of thesecondary heat exchanger 718, namely, within a space generally boundedby the perforated cover plate 732. In some cases, the above-describedsecondary heat exchanger header plate 728 may comprise a substantiallyplain plate of material requiring no special tooling.

Referring now to FIGS. 21-23, an oblique partial view, an obliquepartially exploded view, and an orthogonal right side view ofalternative embodiment of a furnace 800 are shown, respectively. Thefurnace 800 is substantially similar to furnace 100 insofar as itgenerally comprises burner assemblies 814, primary heat exchangers 816,a secondary heat exchanger 818, a fan 824, and a cold header 826. Thisembodiment comprises a secondary heat exchanger header plate 828 towhich secondary heat exchanger tubes 830 are joined and/or through whichsecondary heat exchanger tubes 830 extend through. In this embodiment,the secondary heat exchanger tubes 830 extend through the secondary heatexchanger header plate 828 and are flanged on the ends and/or swaged. Inthis embodiment, a perforated cover plate 832 is captured between afirst seal 834 and a second seal 836. The first seal 834 is capturedbetween the header plate 828 and the perforated cover plate 832. Thesecond seal 836 is captured between a lower portion of the perforatedcover plate 832 and a hot header collector box 842 as well as betweenthe hot header collector box 842 and an upper portion of a hot headerprimary plate 838. A third seal 840 is captured between the hot headerprimary plate 838 and the secondary heat exchanger header plate 828. Insome cases, the above-described embodiment may allow improvedredirection of circulation air from the circulation blower output tocool the hot header collector box 842 by increasing flow through a space844 behind the hot header collector box 842. Further, theabove-described embodiment may allow less expensive insulation to beutilized within a cabinet 846 of the furnace 800.

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure.

Alternative embodiments that result from combining, integrating, and/oromitting features of the embodiment(s) are also within the scope of thedisclosure. Where numerical ranges or limitations are expressly stated,such express ranges or limitations should be understood to includeiterative ranges or limitations of like magnitude falling within theexpressly stated ranges or limitations (e.g., from about 1 to about 10includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13,etc.). For example, whenever a numerical range with a lower limit,R_(l), and an upper limit, R_(u), is disclosed, any number fallingwithin the range is specifically disclosed. In particular, the followingnumbers within the range are specifically disclosed:R=R_(l)+k*(R_(u)−R_(l)), wherein k is a variable ranging from 1 percentto 100 percent with a 1 percent increment, i.e., k is 1 percent, 2percent, 3 percent, 4 percent, 5 percent, . . . 50 percent, 51 percent,52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99percent, or 100 percent. Moreover, any numerical range defined by two Rnumbers as defined in the above is also specifically disclosed. Use ofthe term “optionally” with respect to any element of a claim means thatthe element is required, or alternatively, the element is not required,both alternatives being within the scope of the claim. Use of broaderterms such as comprises, includes, and having should be understood toprovide support for narrower terms such as consisting of, consistingessentially of, and comprised substantially of. Accordingly, the scopeof protection is not limited by the description set out above but isdefined by the claims that follow, that scope including all equivalentsof the subject matter of the claims. Each and every claim isincorporated as further disclosure into the specification and the claimsare embodiment(s) of the present invention.

What is claimed is:
 1. A furnace, comprising: a primary heat exchangertube; a secondary heat exchanger comprising a plurality of secondaryheat exchanger tubes; a hot header configured to provide a fluid flowpath between an output of the primary heat exchanger tube to an input ofthe secondary heat exchanger; and a perforated fluid flow plate disposedat least partially within the hot header.
 2. The furnace of claim 1,wherein the perforated fluid flow plate comprises at least oneperforation that is misaligned relative to the secondary heat exchangertubes.
 3. The furnace of claim 1, wherein the perforated fluid flowplate comprises a profile configured to minimize pooling of condensatewithin the hot header.
 4. The furnace of claim 1, further comprising aseal configured to minimize pooling of condensate within the hot header.5. The furnace of claim 1, further comprising a seal that extends overboth the perforated fluid flow plate and a primary plate of the hotheader.
 6. The furnace of claim 5, wherein the primary plate of the hotheader is associated with an output end of the primary heat exchangertube.
 7. The furnace of claim 6, further comprising a seal between aheader plate of the secondary heat exchanger and the perforated fluidflow plate.
 8. The furnace of claim 7, further comprising a seal betweenthe primary plate of the hot header and the header plate of thesecondary heat exchanger.
 9. The furnace of claim 1, further comprisinga gasket disposed within the perforated fluid flow plate.
 10. Thefurnace of claim 9, wherein the gasket is configured to minimize poolingof condensate within a space bounded by the perforated fluid flow plate.11. An HVAC system, comprising: a primary heat exchanger tube; asecondary heat exchanger comprising a plurality of secondary heatexchanger tubes; a hot header configured to provide a fluid flow pathbetween an output of the primary heat exchanger tube to an input of thesecondary heat exchanger; a perforated fluid flow plate disposed atleast partially within the hot header; an inducer motor configured todraw fluids from the primary heat exchanger tube to the secondary heatexchanger; and a circulation blower configured to selectively causecirculation air to flow from contact with the secondary heat exchangerto contact with the primary heat exchanger tube.
 12. The furnace ofclaim 11, wherein the perforated fluid flow plate comprises at least oneperforation that is misaligned relative to the secondary heat exchangertubes.
 13. The furnace of claim 11, wherein the perforated fluid flowplate comprises a profile configured to minimize pooling of condensatewithin the hot header.
 14. The furnace of claim 11, further comprising aseal configured to minimize pooling of condensate within the hot header.15. The furnace of claim 11, further comprising a seal that extends overboth the perforated fluid flow plate and a primary plate of the hotheader.
 16. The furnace of claim 15, wherein the primary plate of thehot header is associated with an output end of the primary heatexchanger tube.
 17. The furnace of claim 16, further comprising a sealbetween a header plate of the secondary heat exchanger and theperforated fluid flow plate.
 18. The furnace of claim 17, furthercomprising a seal between the primary plate of the hot header and theheader plate of the secondary heat exchanger.
 19. The furnace of claim11, further comprising a gasket disposed within the perforated fluidflow plate.
 20. The furnace of claim 19, wherein the gasket isconfigured to minimize pooling of condensate within a space bounded bythe perforated fluid flow plate.